The present invention relates to a device for supplying secondary air to the intake manifold of an internal combustion engine during deceleration of the engine so as to compensate for the temporary reduction of air/fuel ratio during deceleration of the engine, and, more particularly to an arrangement of a deceleration compensating air control valve for controlling such a secondary air supply relative to the intake air cleaner for the engine.
It is already known and practiced to incorporate in the intake system of an internal combustion engine for an automotive vehicle a deceleration compensating air supply system which supplies secondary air into the intake manifold of the engine during its deceleration, in order to compensate for the temporary reduction of air/fuel ratio of the intake fuel-air mixture which occurs during deceleration of the engine. Such a system generally includes a vacuum-controlled valve having a diaphragm means adapted to be operated by intake manifold vacuum and a valve structure which opens a secondary air control port provided in a secondary air supply passage leading to the intake manifold of the engine when the intake manifold vacuum supplied to the diaphragm means increases beyond a predetermined value.
Conventionally, such a control valve has been mounted on the outside wall of the engine, and has been equipped with its own air filtering means. This conventional structure has the disadvantages in that it requires a relatively large space adjacent to the engine for mounting not only the deceleration compensating air control valve itself but also the air filtering means for the valve which is generally bulky, and that the air filtering means requires periodical cleaning, thereby adding an item of maintenance required. Further, such a deceleration compensating air supply system having its own air filtering means generates a suction noise when air is inhaled therethrough, and increases the total noise level of the engine.